1. Field of the Invention
The present invention relates to improving the fatigue life of a component such as an elongated bar, and more particularly pertains to improving the bar life by heating and thereafter quenching the bar as the bar is being stretched which provides residual compressive forces in an outer annulus of the bar after the stretching forces are released.
2. Description of the Prior Art
George Joseph U.S. Pat. No. 4,131,491 discloses a torsion bar and method of making the bar. The bar is through hardened to provide the desired core hardness and is thereafter induction heated followed by quenching to cause the outer surface or case to be hardened and to expand thereby providing high compressive stresses near the surface. However, the bar is not stretched during the induction heating and quenching process.
Blunier U.S. Pat. No. 4,141,125 discloses a method of mounting track pins by heating the ends of track pins above the critical temperature of steel and then quenching. The ends of the track pins are increased in volume by the process and are thus retained in the bores of the track links.